| 摘要: | 摘要
每年春季中南半島旺盛的生質燃燒(biomass burning, BB)受到盛行西風傳輸到東亞，傳輸煙團沿途對於太陽輻射的直接和間接效應影響環境重大。本研究於2019年春季與秋季，在鹿林山大氣背景監測站(海拔2,862公尺)進行大氣氣膠採樣，以解析東亞受中南半島BB煙團傳輸影響和背景大氣氣膠水溶性有機碳(water-soluble organic carbon, WSOC)、二元酸及其鹽類、單醣脫水醣類、似腐植質物質(humic-like substance, HULIS)特性。
春季BB氣流軌跡類型有較高的PM2.5 WSOC/OC，代表BB煙團有機氣膠較易溶於水形成雲滴，影響環境變遷。草酸及其鹽類(oxalate, C2)為二元酸及其鹽類的主要成分，BB煙團是C2的主要來源之一。左旋葡聚糖是單醣脫水醣類的主要成分，左旋葡聚糖和甘露聚醣比值顯示春季BB氣流軌跡類型氣膠較多來自硬木燃燒，春季PM10-2.5阿拉伯醣醇(arabitol)濃度在適合真菌孢子生成條件下高於其他天氣條件，甘露醇(mannitol)則未如預期有較高濃度。春季HULIS來自生質燃燒和二次形成，BB氣流軌跡類型HULIS占PM10 OC濃度的38.2%。
秋季PM2.5 WSOC是OC主要成分，受BB影響程度較低，以二次反應生成為主，PM10-2.5 WSOC濃度可能也受二次反應影響。PM2.5二元酸及其鹽類來自一次排放較多，相對地，PM10-2.5受到較明顯的光化學二次反應影響。PM2.5 mannitol平均濃度較左旋葡聚醣高，且在多數日期都有較高濃度，可能是受到真菌孢子等生物氣膠的影響。秋季HULIS氣膠來自二次形成，HULIS在PM¬10和OC的質量濃度占比都較春季低。
本研究觀測期間，鹿林山春季受中南半島生質燃燒煙團傳輸影響，氣膠各化學成分濃度普遍較秋季觀測期間高。秋季氣膠呈現背景大氣特性，氣膠生成受人為污染排放和二次光化學反應影響。
關鍵詞：高山測站、氣膠微量有機成分、生質燃燒氣膠。
;Abstract
The vigorous biomass burning (BB) of Indochina is transported to East Asia by the prevailing westly wind every spring. The transporting BB smoke along the way caused direct and indirect solar radiation effects on the environment significantly. This study collected atmospheric aerosol at the Mt. Lulin atmospheric background station (2,862 meters above sea level) in spring and autumn 2019 to characterize water-soluble organic carbon (WSOC), diacids and their salts, monosaccharide anhydrosugars, humic-like substances (HULIS) of atmospheric aerosol under the influence of transported BB smoke from Indochina and background air in East Asia.
The BB airflow trajectory type in spring had a higher PM2.5 WSOC/OC, which implied that the organic aerosols from BB transported smoke were more water-soluble to form cloud droplets, and thus affecting environmental changes. Oxalic acid and its salts (oxalate, C2) are the main component of diacids and their salts. BB transported smoke was one of the C2 major sources. Levoglucosan is the main component of monosaccharide anhydrosugars. The ratio of levoglucosan to mannosan indicated that the aerosol from BB airflow type in spring was mostly contributed by hardwood burning. The spring PM10-2.5 arabitol concentration was found higher in suitable growth conditions for fungal spores than in other weather conditions. However, mannitol did not have a higher concentration as expected. Spring HULIS came from BB and secondary formation with the BB airflow trajectory type accounted for 38.2% of the PM10 OC concentration.
Autumn PM2.5 WSOC was the dominant fraction of OC, mainly from secondary formation and with lesser influence from BB. PM10-2.5 WSOC concentrations may also be contributed from secondary reactions. The PM2.5 diacids and their salts were more contributed by primary emissions. In contrast, PM10-2.5 was obviously influenced more by photochemical secondary reactions. The PM2.5 mannitol average was higher than that of levoglucosan and was higher on most sampling days, which may be affected by bioaerosols such as fungal spores. Autumn HULIS came from secondary formation, and the ratios of HULIS in PM10 and OC were lower than those in spring.
During the observation period of this study, the spring concentrations of various chemical components at Mt. Lulin were pervasively higher than that in autumn due to the influence of the BB smoke transported from Indochina. Autumn aerosols presented the characteristics of the background atmosphere, aerosol formation was affected by primary anthropogenic pollution emissions and secondary photochemical reactions.
Keywords: Moutain station, Aerosol trace organic components, Biomass burning aerosol |
